In general, there is known a hybrid construction machine provided with a motor generator that is jointed mechanically to an engine and a hydraulic pump, and an electricity storage device such as an lithium ion battery or capacitor and the like (for example, refer to Patent Document 1). In this hybrid construction machine, the motor generator has a function of charging power generated by a driving force of the engine in the electricity storage device or assisting in the engine by power running which uses power of the electricity storage device. Many hybrid construction machines are provided with an electric motor separated from the motor generator, and the electric motor acts for or assists in an operation of a hydraulic actuator. For example, at the time of performing a revolving operation by the electric motor, the electric motor performs or assists the revolving operation of an upper revolving structure by power supply to the electric motor, and braking energy at a revolving stop is regenerated to perform a charge of the electricity storage device.
Here, Patent Document 1 discloses the configuration of highly efficiently collecting regeneration energy by appropriately controlling an electricity storage amount in the electricity storage device. In this case, the next operation of a working mechanism or the upper revolving structure is estimated based upon operating information of an operator and a target electricity storage amount is set based upon an estimation value of the regeneration power calculated from the estimated operation.